Manufacture of paper



Patented Eco, 1, 1931 PATET orrics HARQLD coarser RAFTON', Z5 ANDQVER,MASSACHUSETTS, ASEJGNQR TQ BAI'FQLD PROCESS CORPOMEIUN, A CQRIEORATION0F MASSfiGE'USFETfi l lo Drawing,

This invention relates to the manufacture taining alkaline filler.

The principal object of this invention is to provide a novel method ofusing starch in paper made With alkaline filler.

An important object is to provide a method of using starch which willmeasurably avoid decomposition oi the starch in the paper-mahingprocess.

A further object is to provide a method oi using starch wherein themaximum Viscous properties of the starch are retained.

Other objects arid advantages of tli vention will become apparent duringcourse of the following description.

Starch has been used for years as a constituent of paper mixes to impartstitiening, a firmer "feel, and the like qualities paper made therewith,

As I hays disclosed in thy copending aopli cation Serial No, 202,453,filed June 29, 1927, starch is also particularly valuable incerta casesWhere alkaline iillersare used in pa making, for substantiallyeliminating the loam-forming tendency f om otherwise foam-forming mixes.lln the alcove referred to application the use starch in conjunctionwith alum is also recommended,

Where starch has heen employed heretofore as a constituent of papermixes it has been the customary practice to mix it a compounding and/ortreating device, such as a heater or the hire, with an aqueoussusoension of fihrous material and such other material as may heemployedv in paperrnaking such as filler, size, for example rosin size,size preci itant, for example alum, tinting and the lil e. This mixusually has a dry solid con tent of approximately 5%, more or less. Themix after subjection to suficient treatment in the heater, is thenordinarily discharged into a container commonly called a heater chest,additional Water usually losing added. Thereafter the mix may hetransferred from may be approximately point commonly being referred toas the coir:-

the beater chest to a suitable refining en ine, usually a Jordan, at adry solid content W ich 131 the neighborhood Application filed February5, 1930. Serial Ito. 426,199,

of 4%. ln common practice the mix is this point usually diluted somewhatby the addition of Water, and the diluted mix alter jordaning isordinarily conducted from the Jordan to another container commonly knownas machine chest, From the inschine chest the mix is transferred to apoint near the Web forming end of a paper machine Where it is largelydiluted' with Water, this mg hex, Water hein here added ordinarily insuch to provide a dry content zimat to 1% or slightly higher, hutcasually not in excess of li The in such h1g3 dilute condition is thenpasse 1 rs or the like desired d 6;. ough screens and through the H thepaper niachin on to the rose is wire, into a rat, dc 1 ing' upon Wl aFonrdrinier or a cy machine is i ycd; and during this passage additionalamounts water are ads 5. in the form a sprays or otherwise.

This exact procedure is not always ioh lowed hut in some ins nces ismodified i accordance with the of paper lasing made. F or example, inthe manufacture of certain types of paper the heating process is almostit not entirely dispensed with, the ingredients losing merely mixedtogether prior to jordaning. some instances the step of rehning orordanine may be partially if not Wholly dispensed with. Moreover in somecases the arrangement or? steps is difierent; for example, the jordaningmay take place subsequent to the machine chest, the stool: passingdirectly from the Jordan to the mixing box. gometimes also thearrangement.

till

- subject to'attack by molds and the like, and

in the'course of its assage through the beater, chests, and J or an, upto the point of dilution, the length of time is such that. the

starch remains sufficiently long, in the system for thesedeterioratingagencies to act thereon to a'considerable extent. Thedeterioration seems to be particularly pronounced in certain instanceswhere the system is alkaline as would be the case where alkaline filleris employed, particularly where it is added in the beater. Theputrescent condition is aggravated if there be present in the inix otherputrescible materials such as old paper stock (reworked old papers),particularly if such contain reworked coated papers containing casein.If in addition there be other elements which prolong the continuance ofcontact of the starch with the other ingredients of the mix such as iscustomary in modern papermaking equipment, this tendency towarddecomposition is much more manifest. An example of such elements whichmaintain the other ingredients of the mix in contact with the starch forlonger times is where recovery systems are used in the white watercycle. Sedimentation systems are common for use on the excess whitewater,

and in such instances the recovered stock,

which in this case would contain starch, is returned to the papermakingoperation, commonly to the beater. Another type of recovery systemcommonly used and which illustrates the point satisfactorily is thefiltration type whichngrmally mixes the excess white water from themachine with the so-called sweetener stock usually taken fromv theheater or machine chest, and returns the material filtered from theexcess white water together with the sweetener stock back into one orthe other chests. This filtration cycle, as is apparent, returns part ofthe starch which would ordinarily escape with the white waters back intothe papermaking operation and thus prolongs the contact of the starchwith the other constituents of the mix and promotes its decomposition.

As a result of the decomposition, not only is the starch in partdeteriorated or destroyed, but there is a considerable opinion that suchdecomposition of the starch is very njurious in promoting slime in thepaper and also as being in certain cases an agency which promotes theformation of soft lumps on the paper machine, which in turn greatlyinterfere with production and reduce the quality of the paper made undersuch conditions.

Another disadvantage inherent in the method heretofore employed in usingstarch is the fact that even though the system were kept entirelysterile so that no growth of molds or micro-organisms could take place,

nevertheless the constant agitation such as c less proportional to theamount of agitation it receives.

Ihave discovered that the disadvantages inherent in the method ofutilizing starch hitherto. employed, can be overcome to a very greatextent by minimizing the time and/or intimacy of contact of the starchwith the other constituents of the paper mix and I have deviseda methodwhereby my discovery can be practically utilized in the papermakingoperation.

Briefly, I add the starch to the mix at a point late in the papermakingprocess, for example, subsequent to the passage of the mix through themachine chest and preferably at the wet end of the paper machine,whereby the time of'contact of the starch with the other constituents ofthe mix is greatly minimized. Moreover the'addition of the starch in thedilute stage of the papermaking process acts to decrease greatly theintimacy of contact of the constituents of the mix and thereby preventsdeterioration of the viscous quality of the starch by diminishing thefrictional action to which the starch is subjected.

Of course, in certain cases such as where the refining engine is placedbetween the final stock chest and the paper machine, the starch may beadded subseguent to the delivery of the stock from this nal chest. Inthis case the Jordan acts as an eflicient incorporating means for thestarch with the paper mix, and inasmuch as the time of contact in theconcentrated condition. is only very brief, the results are in certaincases wholly satisfactory; However, in most cases I have found itpreferable to effect the mixing of thestarch at the wet end of the papermachine, usually at the mixing boxor at any point which may beconvenient prior to the delivery of the mix on to the Web-formingdevice.

nesaeos It will thus be apparent that my method of utilizing starch inthe papermaking process avoids to a great extent thedeterioratinginfiuences formerly inherent in the method of adding starchin the beater, removes the starch as a source of putrescence from theearlier part of the papermaking operation, tends to prevent in certaincases in a consid erable measure the formation of slime and lumps in thepapermaking process, and prevents the deterioration of the valuableviscous quality of the starch owing to the prevention of prolongedagitation of the starch in contact with the other constituents of themix.

As will be apparent this makes for the more efiicient use of the starchand lesser amounts than formerly were required to give certain desiredproperties to the paper mix or resulting paper can now he used. It isthus apparent that my process is very beneficial from the standpoint ofstarch economy.

In those cases as indicated above where settling or filtration cycles onthe excess white waters return the material recovered from the excesswhite water to the earlier stage in the process either the heaters as issometimes done with settling systems or to the chests as is sometimesdone with filtration systems it will be apparent that part of the starchin the furnish will he returned to an earlier stage of the process.This, as has been indicated ahove, is not theoretically the mostadvantageous procedure. However, owing to fact that the starchoriginally introduced is highly viscous owing to undeterioratedcondition, as well as to the fact a lesser amount of starch may heemployed than for merly, less of the starch than was formerly the casewill tend-to be present in the white water coming from the machine andthus only a relatively small quantity will he reintroduced at an earlierstage in the process. As this quantity is small compared with theoriginal amount of starch employed, and especially it it hereintroduced, as is preferable, in the latter part of the system such asin the machine chest, serious detriment will be incurred from thepresence of this minor quantity of starch in the system prior to thepassage of the mix from the machine chest. However, if it he feasible,it is especially advantageous in this connection to employ the machinecycle disclosed in my copending application Serial No. 4238,6544, filedMarch 24, 1930, whereby substantially all of recovered material isreturned to the papermaking operation just prior to or at the dilutestage.

y invention may be conveniently employed in the manufacture either ofsized or substantially unsized papers. Moreover, it may be carried outsatisfactorily in connection with the processes disclosed in various ofmy copending applications, that is, the starch may be the onlymaterialadded at the wet Substantially 'u/naz'zed paper Pounds Sulphite pulp 350Soda pulp 435 Reworked old magazine papers (deinked) 600 Broke(defective paper to bereworked) 180 Alkaline filler (e. g. llaCO Mg (@H)720 Alum '50 Starch 75 In the above furnish the starch is added,preferably continuously, at the wet end of the paper machine. lhe fillerand/or alum may either be added in the heater with the fibrous.constituents, or at the Wet end of the paper machine.

Another suitable furnish is as follows:

Sized paper Pounds Sulphiteand soda pulps 2709 Size (e. rosin sis-c l5Alkaline filler (e. g. waC@ l /lg(@ll) 300 Size precipitant (e. alum)Starch 5G in the above furnish starch is added, pref erablycontinuously. at the wet end of the paper machine. "ei erahly least oithe alum should also be added at that point. T he iiller and/or the sizemay either he added in the heater, or at the wet end of the papermachine.

in ooth the above furnishes weights of the size and alkalinefiller'refer to the bone dry basis; the weights of all otherconstituents refer to the air dry basis.

It will be understood of course that the above furnishes intended asillustrative only and in no sense as restrictiye, as widely (litteringfurnishes give satisfactory results. The starch used may vary widely inamount. Practically speaking, however, although i do not restrict myselfthereto,i less than one percent. has lout little effect on the finishedpaper and starch is seldom use in lesser amount in papermaking.

As is well known, starch is customarily employed in the papermakingprocess by treating raw starch in such a manner as to produce a viscoussolution. This may be suitably accomplished by heating starch and Waterto the point where the starch is cooked, i. e., where it becomes asubstantially homogeneous viscous colloidal solution. This solution isthen usually allowed to cool. It is in such condition that 1 preferablyemploy starch in my process. However, starch, i. e.,

unmodified starch, is not always emplo ed in papermaking; sometimes theso-ca led modified starches are used. A great variety of these withdifierent properties are on the market, e. g., some are dlrectl solublein cold water, others give thin boilmg solutions. My process, as will beapparent, is also useful-with modified starches for although thequestionv of maintaining the viscosity ma not be of such greatimportance with suc this group may be mentioned calcium car-.

bonate, of which lime mud from the causticizing process is one form;calcium carbonate magnesium basic carbonate employed in the paperdisclosed in my U. S. Patent No. 1,595,

416, dated August 10, 1926; calcium carbonate magnesium hydroxidedisclosed in my U. S. Patent No. 1,415,391, dated May 9, 1922; and othersubstantially water insoluble normal or basic carbonates of alkalineearth metals, (which expression is herein intended to includemagnesium), or compounds,

'double salts, or physically associated mixtures of these with one ormore other acid soluble materials of a substantially water insolublenature.

By the term alkaline filler I also intend to include fibrous materialand/or other material such as paper coating constituents or the likecontaining one or more compounds of the character referred to, such asold papers or similar papers, broke, or the like.

When I use the word paper herein, I use it in the broad sense to includeproducts of manufacture of all types and of all weights and thicknesses,'which contain as an essential constituent a considerable amount ofprepared fibre and which are ca able of being produced on a Fourdrinier,cy inder, or other forming, felting, 'shaping or molding machine.

By the term wet end of the paper machine, I intend to include thoseinstrumentalities employed in paper manufacture by which and/or in whicha relatively concentrated paper mix is diluted, and treated, conveyed orfed up to the point of web-formation, such as the mixing box, regulatingand proportioning devices, rifilers, troughs, screens, head boxes,inlets, and the like, including also instrumentalities used in the whitewater cycle.

In my copending application Serial No.

' 304,167, filed September 5, 1928, I have disclosed but not claimed theaddition of starch to a fibrous mix at the wet end of the paper machinein the manufacture of paper filled with an alkaline filler.

In my copending application Serial No. 304,175, filed September 5, 1928,I have disclosed and claimed a method for sizing paper filled with analkaline filler in which size such as rosin size and size precipitantsuch as alum are mixed in the presence of starch, and the resultingproduct is added to the fibrous mix at the wet end of the paper machine.Moreover, in my copending applica tion Serial No. 319,721, filedNovember 15, 1928, I have disclosed and claimed a method ofincorporating into pa er filled with alkaline filler an inorganic al alimetal salt with a pH value greater than 7.0, for example sodium silicatewhich is precipitable by material which depresses its hydro 1 ionconcentration, by mixing said alkali metal salt with a precipitanttherefor in the presence of starch, and adding the resulting product tothe fibrous mix at the wet end of the paper machine. I therefore excludefrom the scope of the present specification and claims the addition ofstarch, in the manufacture of paper filled with alkaline filler, to afibrous mix under conditions favoring the minimizing of the time and/orintimacy of contact of the constituents of the mix in the cases wheresuch starch has had previously added to ita size or an alkali metal saltsuch as described in this paragraph, together with a precipitanttherefor.

While I have described in detail the preferred embodiment of myinvention, it is to be understood that the details of procedure, theproportions of ingredients, and the arrangement of steps may be widelyvaried without departing from the spirit of my invention or the scope ofthe subjoined claims.

I claim:

1. The step in the method of manufacturing paper filled with alkalinefiller comprising adding starch to a fibrous mix under conditionsfavoring the minimizing of the time of contact of the starch with theconstituents of the mix. 1

2. The step in'the method of manufacturing pa er filled with alkalinefiller comprising ad ing starch to a fibrous mix under conditionsfavoring the minimizing of the time and intimacy of contact of thestarch with the constituents of the mix.

3. The step in the method of manufacturing paper filled with alkalinefiller comprising adding starch to a fibrous mix subsequent to thepassage of the mix from the machine chest. 7

4. The step in the method of manufacturing paper filled with alkalinefiller comprising adding starch to a fibrous mix at the wet end of thepaper machine.

5. The step in the method of manufacturing paper filled with alkalinefiller comprising adding starch and alum to a fibrous m1x at the wet endof the paper machine.

6. The method of manufacturing paper filled with alkaline fillercomprising adding starch, alum, and alkaline filler to a fibrous mix atthe. wet end of the paper machine,

and thereafter making paper therefrom.

7. The method of manufacturing paper filled with alkaline fillercomprising adding starch, alum, alkaline filler, and size to a fibrousmix at the wet end of the paper machine, and thereafter making papertherefrom.

8. The step in the method of manufacturing paper filled with alkalinefiller comprising calcium carbonate, which comprises adding starch to afibrous mix under conditions favoring the minimizing .of the time ofcon- 2 tact of the starch with the constituents of the mix.

9. The step in the method of manufactur ing paper filled with alkalinefiller comprising calcium carbonate and magnesium compound, whichcomprises adding starch to a fibrous mix under conditions favoring theminimizing of the time of contact of the starch with the constituents ofthe mix.

10. The step in the method of manufacturing paper filled with alkalinefiller comprising calcium carbonate magnesium hydroxide, which comprisesadding starch to a fibrous mix under conditions favoring the minimizingof the time of contact of the starch with 3 the constituents of the mix.

11. The step in the method of manufacturing paper filled with alkalinefiller comprising calcium carbonate maghesium hydroxide, whichcomprises'adding starch to a fibrous mix under conditions favoring theminimizing of the intimacy and time of contact of the starch with theconstituents ofthe mix.

12. The step in the method of manufacturing paper filled with alkalinefiller comprising calcium carbonate magnesium hydroxide, which comprisesadding starch to a fibrous mix at the wet end of the paper machine.

13. The step in the method of manufacturing paper filled with alkalinefiller, comprising adding starch at the wet end of the paper 'macllilineto a fibrousmix containing old paper stoc 14. The step in the method ofmanufactur-" ing paper filled with alkaline filler, comprising addingstarch at the wet end of the paper machine to a fibrousmix containingcasein bearing constituent.

15. The method of minimizing the putrescence of starch in themanufacture of paper L filled with alkaline filler comprisingwithholding the addition of the starch until late in the process ofstock preparation.

16. The method of manufacturing paper filled with alkaline filler,comprising mixmg fibrous material and alkaline filler in the beater, andadding to the resulting mix starch at the wet end of the paper machine.

In testimony whereof I aflix my signature.

HAROLD ROBERT RAFTON.

